COMMUNITY SUCCESSION AND DEVELOPMENT 



579 



Numerous direct and indirect human quence of man's urbanization, draining of 

 agencies alter the course of community natural water reservoirs, construction of 

 development and succession, such as fires, canals and roads, strip mining, overcultiva- 



:>r • *- 



Fig. 216. An example of the influence of man on the development of communities: photo- 

 graphs of overgrazed and ungrazed grassland in Texas (above), and grazing cattle in New 

 Mexico (below). (Courtesy of W. P. Taylor and the U. S. Soil Conservation Service.) 



flooding (as a consequence of impairment tion and overgrazing (Fig. 216). Such 

 of watershed), pollution, impairment or secondary effects may be direct, as in forest 

 destruction of communities as a conse- fires, or indirect, as in the "dust bowl" 



